April 15-17

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Abstracts

Author: David R Hatch
Requested Type: Poster
Submitted: 2019-02-21 22:59:20

Co-authors: M. T. Kotschenreuther, S. M. Mahajan, M. Halfmoon, E. Hassan, G. Merlo, J. Canik, I. Joseph, M. Umansky, W. Guttenfelder

Contact Info:
University of Texas at Austin
2515 Speedway C1500
Austin, TX   78712
USA

Abstract Text:
The properties of an edge transport barrier are governed by three complex and sensitively interconnected components: (1) pedestal MHD stability, (2) divertor and SOL conditions, and (3) the residual pedestal transport. The residual transport remains, perhaps, the least understood component of the edge system. Transport, in combination with the corresponding sources and sinks, determines the heating power necessary to achieve a given pedestal temperature; the inter-ELM evolution of pedestal density and temperature profiles, which ultimately determines the operating point at which an ELM is triggered; and the accessibility and properties of ELM-free regimes. This presentation will report on the ongoing FY19 theory performance target (TPT), whose goal is to identify the turbulent transport mechanisms, along with the corresponding heat and particle sources, that govern pedestal dynamics. This will be accomplished via two sets of computational tools: (1) gyrokinetic codes (GENE and CGYRO), which can analyze the instabilities that arise in the pedestal, and (2) edge codes (SOLPS and UEDGE), which, when operated in interpretive mode, can provide the best possible estimate of particle and heat sources—e.g., the ionization density source and the atomic energy loss channels due to ionization, charge exchange, and radiation. Such information, in combination with available fluctuation data, and observed inter-ELM profile evolution, provides powerful constraints on the candidate instabilities that may govern pedestal transport.Comparisons will be made with discharges spanning multiple devices and exploring a wide range of parameters, modes of operation, wall materials, etc.. This combined analysis of instabilities / transport and edge modeling is unprecedented and, when applied to a wide range discharges, promises to qualitatively advance our understanding of pedestal transport.

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